Nudibranchs and sponges contain substances that lower blood pressure in mammals and have negative inotropic and chronotropic effects on isolated hearts. The objective is to purify and characterize these uninvestigated compounds that resemble nucleosides both pharmacologically and chemically. They are low molecular weight, water-soluble and heat-stable. We propose to extract them with solvents and to purify them by column and thin layer chromatography. Purification would be checked by bioassay. The effects of highly purified compounds would be investigated for cardioactive properties on perfused guinea pig hearts and isolated atria and by electrocardiograms in mammals. Rats would be used for study of hypotensive effects and rabbit intestine for smooth muscle activity. Perfused rabbit ears would be used for study of vasodilator activity. We would attempt to determine chemical structure principally from mass and nmr spectral studies.